Newer and safer forms of stem cell therapy will likely overtake
research into the use of human embryonic stem cells, the scientist
whose team cloned
Dolly the sheep
told his peers at a stem cell conference in La
Direct "reprogramming" of adult cells into the type needed for
therapy is gradually becoming a reality, Ian Wilmut told an
audience of several hundred at the Salk Institute at the annual
Stem Cell Meeting on the Mesa. Such a feat was once thought
impossible, but in recent years it has been demonstrated in at
least two publications, he said.
These reprogrammed cells appear likely to provide the
anticipated benefits of embryonic stem cells without their risks,
such as forming tumors. That risk will make government very
reluctant to approve the use of cells derived from embryonic cells
when a safer alternative is feasible, said Wilmut, whose team of
researchers cloned Dolly the sheep nearly 15 years ago.
With its $3 billion stem cell program, California placed a big
bet on the field known as regenerative medicine, hoping for a big
payoff in improving health and boosting its large biotech
industry. A major goal is to grow replacement tissues or organs
for insulin-producing cells that can be transplanted into
diabetics. San Diego academic centers play a big part in that
effort. They recently opened a new $127 million stem cell research
Embryonic stem cells can grow into nearly any cell in the human
body. Artificial embryonic stem cells, or so-called induced
pluripotent stem cells, act in much the same way.
This plastic quality attracts scientists, who foresee
transforming them into nerve cells to repair brains in Parkinson's
disease patients or insulin-producing cells for diabetics whose own
insulin cells have been destroyed.
But it's been unclear which types of stem cells would prove most
useful: the "adult" kind that have a more limited potential to
change, or the embryonic kind. The emergence of direct
reprogramming provides a promising new option scientists should
consider, Wilmut said.
"I'm not quite sure why this hasn't been pursued more actively,"
It is difficult to achieve purity in embryonic and induced
pluripotent stem cells because they are prone to forming
Direct reprogramming of cells from one type to the other avoids
that danger, because the cells never enter the pluripotent stage to
begin with, Wilmut said.
Direct cell reprogramming didn't exist when California voters
approved the stem cell program in 2004 with the passage of
Proposition 71. That program was mainly aimed at funding embryonic
stem cell research the federal government wouldn't fund.
However, the program can also fund research with other types of
stem cells, such as "adult" cells from umbilical cord blood.
The use and value of embryonic stem cells is an intensely
Many people object to their use because human embryos, which
they consider human individuals, are killed to get the cells.
Critics also point to the success of adult cells in approved
therapies, while no therapy with embryonic stem cells has yet been
Three treatments with embryonic stem cells are in clinical
testing in people.
CORRECTION: An earlier version of this story said incorrectly
that there was one clinical trial of embryonic stem cell